JPH07220913A - Magnetic steel plate excellent in magnetic characteristic - Google Patents

Abstract

PURPOSE:To provide products of oriented magnetic steel plates having an iron loss reducing effect after stress easening annealing, when they are practically usable, by solving a problem on the shape of recessed grooves of a tooth-shaped roll formed by a method by the pressure method or by chemical etching. CONSTITUTION:The surface of an oriented magnetic steel plate has traces of a continuous pattern, and the rear of the steel plate is flat. The average diameter of the craters formed on the surface by emitting a Q switch CO2 laser beam is 100-200mum, and the depth is 10-30mum. They are uniformly arranged so that they may be 3-10mm in a rolled direction and that the ratio of hole processing (hole interval/hole diameter) to be specified by the hole diameter and the hole interval may be 1.0 or less. The magnetic steel plate is an oriented magnetic steel plate excellent in magnetic characteristics, and its iron loss reducing effect is not lost even by stress easing annealing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet having excellent iron loss characteristics capable of withstanding the stress relaxation annealing (SRA) of grain-oriented electrical steel sheet, and particularly, by pulsed CO ₂ laser beam irradiation. It relates to a grain-oriented electrical steel sheet with low iron loss, whose magnetic characteristics are greatly improved by the crater shape of the formed metal and the continuous pattern of its arrangement.

[0002]

2. Description of the Related Art It is desired to reduce iron loss of grain-oriented electrical steel sheets from the viewpoint of energy saving. As a method, a method of subdividing a magnetic domain by laser irradiation has already been disclosed in Japanese Patent Publication No. 58-265405. The reduction of iron loss by the method introduces stress strain into the grain-oriented electrical steel sheet by the reaction force of the thermal shock wave generated by irradiating the laser beam, and subdivides the magnetic domain to suppress the increase of hysteresis loss and suppress the eddy current. This is intended to reduce loss. Therefore, the above method can be used for a laminated iron core transformer that does not require strain relief annealing, but for a wound iron core transformer that requires stress relaxation annealing treatment, the strain introduced by the laser during annealing disappears, and the magnetic domain subdivision is performed. There was a problem that it could not be used because the activating effect was lost.

On the other hand, as a method for improving the magnetic properties of the grain-oriented electrical steel sheet in which the effect of reducing the iron loss value is retained even after the stress relaxation annealing, a structure that remains in the steel sheet even after the stress relaxation annealing exceeding the stress strain level. Has been devised and variously proposed by introducing a change in magnetic permeability by applying a change in shape or shape to subdivide a magnetic domain.

As an example of reducing the iron loss value which is effective after stress relaxation annealing due to a change in shape, the following is disclosed in which groove-shaped, point-shaped or linear recesses are introduced into a steel sheet. There is.

A Japanese Patent Publication No. 63-44804 proposes a mechanical pressing method. An average load of 70 on a steel plate that has been finish annealed or treated with an insulating coating by a gear-type roll.
When forming a linear or dot-shaped, broken-line-shaped recessed portion of up to 220 kg / mm ² , the temperature of the steel sheet is processed to 50 to 500 ° C. and then heat-treated at a temperature of 750 ° C. or higher to form crystal grains. It is intended to generate fine recrystallized grains to subdivide magnetic domains. This method has stability in machining,
Although there are problems in the manufacturing method such as reliability and complication of the process, the effect of reducing the iron loss value sufficient for a practical level can be expected from the viewpoint of only the magnetic characteristics.

As a similar method, a method for treating grain-oriented electrical steel sheet in which the iron loss improving effect does not disappear even when stress relaxation annealing at 800 ° C. or higher is performed, is described in Physica Scripta., Vol. T2.
4, p.36-41, 1988, there is proposed a method of forming grooves having a depth of 10 to 25 μm at right angles to the rolling direction by using a tooth profile roll. According to this method, it has been experimentally confirmed that the improved iron loss value does not deteriorate even if stress relaxation annealing is performed at 850 ° C. for 4 hours. This method is also a surface contact processing method, and since the electromagnetic steel sheet contains a large amount of Si, the material hardness is considerably high, so that the life of the tooth profile roll is short and the production cost is significantly increased. Despite the above-mentioned problems, the iron loss value reduction effect sufficient for practical use is obtained as a product. Further, the introduction of recesses by a method by chemical etching is disclosed in US Pat. No. 4,750,949, and although there is a problem of low productivity, a sufficient iron loss value reducing effect is obtained here as well.

Further, as a structure in which the core loss reduction effect remains after stress relaxation annealing by introducing a structural change,
Japanese Unexamined Patent Publication No. 59-100222 discloses a method of introducing an artificial grain boundary by locally heat treating a steel sheet after secondary recrystallization annealing to anneal at a temperature of 800 ° C. or higher. . In the method, reduction of the iron loss value is achieved by subdividing the magnetic domains by the artificial grain boundaries introduced into the steel sheet. Since the annealing is performed at a temperature of 800 ° C. or higher, the effect does not disappear due to the strain relief annealing, but the iron loss value reducing effect of the practical level similar to the iron loss value reducing method of introducing the shape change from the examples is obtained. Can't get

Despite the method-related drawbacks described above, the grain-oriented electrical steel sheet in which the iron loss value is reduced by introducing the groove-shaped, point-shaped, or linear shape change of the recess on the surface of the steel sheet is It is a known fact that it is at a practical level as a product from the viewpoint of the size of the reduction range and stability of the reduction situation.

However, the above-mentioned electromagnetic steel sheet having a concave groove produced by the method of mechanical or chemical etching is problematic from the viewpoint of industrial productivity in terms of industrial productivity. There is such a problem.

When the shape of the concave portion formed mechanically is observed in detail, the scratch of the concave portion is introduced into the steel plate having high hardness by the sharp blade type tool, and therefore the concave portion has a cross section as shown in FIG. 3 (A). It is quite sharp at each corner. Alternatively, since the stress is forcibly applied to the steel sheet beyond the elastic region to introduce the recess groove, extra strain is introduced in the vicinity of the recess,
A large residual stress exists, and a convex portion usually exceeding 4 μm occurs on the back surface of the steel sheet. Since this convex portion is formed by the deformation of the elastic region, it remains without disappearing even after the subsequent flattening temperature rising process.
The main purpose of the electrical steel sheet, which has the effect of reducing the iron loss value after stress relaxation annealing, is to use it for the wound core. The steel sheet that has been subjected to the iron loss value reduction processing is processed into the shape of a wound iron core, and then subjected to stress relaxation annealing to remove the extra strain introduced during the winding processing. Therefore, the mechanical processing characteristics of the steel sheet due to the distortion introduced at the time of introducing the concave groove or the shape of the concave groove appear as it is at the time of roll forming.

The electromagnetic steel sheet is a material having a low workability because it contains a large amount of Si in its components, and cracks are caused by a slight cause.
If it is desired to form a wound iron core with a small curvature, the shape of the recess introduced mechanically as described above is sharp at each corner, and the recess is cracked against the electromagnetic steel plate with low workability. There is a problem that cracks occur during the winding process because it becomes the starting point of. Further, as described above, since the convex portion is generated on the back surface of the mechanically formed concave portion, when the wound iron core is manufactured as shown in FIG. Occurs. This causes a problem that the space factor of the steel sheet is reduced and the performance of the iron core is significantly reduced (FIG. 4).

Even in chemical etching, which is another method of introducing the concave groove, the convex portion on the back surface at the time of introducing the concave portion does not exist unlike the mechanical type (FIG. 3 (B)), but the sectional shape of the concave portion does not exist. There is a problem that it is more acute than that of the mechanical type, and the occurrence of cracks during winding is larger than that of the mechanical type.

As described above, the grain-oriented electrical steel sheet having the recessed portion on the surface of the steel sheet, which has the effect of reducing the iron loss value even after the stress relaxation annealing by the conventional method, is practically used due to the characteristics of the machined shape itself. I had a problem with.

[0014]

SUMMARY OF THE INVENTION The present invention solves the problem of the shape of the concave groove formed by the conventional method of pressing the tooth profile roll or the method of chemical etching.
It is intended to provide a product of grain-oriented electrical steel sheet which can be practically used and still has the effect of reducing the iron loss value after the stress relaxation annealing.

[0015]

The present invention is a Q switch C.
The average diameter of the craters formed on the surface of the grain-oriented electrical steel sheet by irradiating with an O ₂ laser is 100 to 200 μm.
And 10 to 30 μm in depth and 3 to 10 in the rolling direction.
mm, with traces of a continuous pattern uniformly arranged in the steel plate width direction so that the crater hole drilling ratio is 1.0 or less, and the steel plate surface is flat, and the effect of reducing iron loss value after stress relaxation annealing The present invention is directed to a grain-oriented electrical steel sheet having excellent magnetic properties, which is characterized by remaining.

[0016]

The present invention will be described in detail below. FIG. 1 shows a Q-switch CO ₂ laser resonator, which is a main component of the method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, which is characterized in that the iron loss value-reducing effect remains after stress relaxation annealing. And the configuration of an optical system for irradiating the electromagnetic steel sheet with the output pulse thereof.

The laser discharge part 2 is a part for supplying energy to the laser gas, which is a CO ₂ laser medium, by discharge excitation in a continuous or pulsed manner, and is composed of a total reflection mirror 3 and a total transmission window 4 which constitute a laser resonator. It is cut off from the atmosphere. A Q-switching device including a confocal telescope 5 and a rotary chopper 6 is installed between the output mirror 7 installed in the atmosphere and the total transmission window 4. The pulsed laser beam 1 extracted from the Q-switch CO ₂ laser resonator is scanned in the plate width direction of the electromagnetic steel plate 10 by the rotary scanner by the polygon mirror 8, reflected by the plane total reflection mirror 11, and is reflected by the parabolic mirror 9. After being focused,
The electromagnetic steel plate 10 is irradiated.

FIG. 2 shows a Q-switch CO ₂ laser pulse waveform when Q-switch oscillation is performed at a pulse repetition frequency of 12 kHz. The initial spike portion is a giant pulse oscillating portion peculiar to the Q-switch laser, and the range of the half value width is 10 nsec or more and 1 μsec or less.
This Q-switched CO ₂ laser pulse has a long tail after the initial spike. The maximum length of this tail portion is about 10 μsec. This is a pulse tail peculiar to the Q-switch CO ₂ laser which is not found in the Q-switch YAG laser. In Q switching using the rotary chopper, the pulse tail length can be shortened by appropriately changing the width of the laser light transmitting slit. The maximum value of the pulse repetition frequency during Q switch oscillation can be realized up to about 100 kHz when Q switch oscillation is performed using a general continuous wave CO ₂ laser. When lowering the frequency below this, 20
In the region up to the pulse repetition frequency of about kHz, the pulse energy and the pulse repetition frequency have an approximately inversely proportional relationship, that is, a constant laser average output is obtained.

The Q switch pulse CO as shown above
_{2 The} iron loss characteristic improvement when the grain oriented electrical steel sheet is irradiated with _two lasers will be described in detail below. First, the hole depth was changed with respect to the hole diameter, and the effect of reducing iron loss was investigated. Although the hole depth was changed when the hole diameter was less than 100 μm, the effect of reducing the iron loss value could not be obtained due to the insufficient magnetic domain subdivision effect, and the iron defined by the ratio of the improved iron loss value to the starting iron loss value was determined. The loss improvement rate was also 5% or less on average.

Next, when the hole diameter is 100 to 200 μm, when the hole depth is 10 to 30 μm, the result that the iron loss value reducing effect does not disappear even after the stress relaxation annealing is obtained, and the result is obtained. A loss improvement rate of 7% or more was stably obtained. The processing conditions at this time were a laser beam diameter of 0.2 mm and a peak power density of 2 × 10 ⁷ W / cm ² to 2 × 10 ⁸ W / cm ² . Regarding the hole depth, when a deeper recess was introduced on the surface of the steel sheet, the magnetic flux density deteriorated, the iron loss reduction effect tended to be unstable, and the iron loss improvement rate was also 5% or less. It is considered that this is because if the strained region formed by laser processing becomes too wide, the magnetic domain subdivision becomes difficult to occur. Further, when the hole diameter exceeded 200 μm, the recesses were formed with varying hole depths, but the magnetic flux density was also deteriorated, and the iron loss reduction effect tended to be unstable, and the iron loss improvement rate was 5%. Fell below%. It is considered that this is because if the strained region formed by the laser processing becomes too wide, the magnetic domain subdivision becomes difficult to occur. Therefore, in order to effectively reduce iron loss, the hole diameter should be 100-200μ.
m, and it is preferable to introduce a recess having a hole depth of 10 to 30 μm.

FIG. 3C is a schematic view showing the cross-sectional shape of the processed hole or groove obtained at this time. The shape of the processed hole is close to a bowl shape determined by the processed hole diameter D and the processed hole depth h. It is considered that this is because the laser energy density at the processing point was higher in the central portion and the evaporation removal phenomenon of the steel sheet started from the central portion. Furthermore, in the present experiment, dry air was blown as an assist gas to the steel plate coaxially with the laser beam in order to promote the removal of the steel plate, but since the gas flow is formed concentrically from the center part of the hole to the outer peripheral part, Promotes the processing of bowls where the center of the hole is deep.
In this way, when the recess is formed in the steel plate by laser processing, the hole processed from the processing process is formed into a bowl shape and has a shape different from the sharp one formed by mechanical or optical etching. . Further, when the condition of the unevenness on the back surface of the steel sheet at this time was examined, there was almost no unevenness due to the influence of the surface processing.

In the method of forming the concave portion by laser irradiation as described above, since the formed concave portion is basically spherical, as described above, it can be a starting point of a crack when the electromagnetic steel sheet after the treatment is roll-formed. There is little nature. Also, since the formation of recesses by laser irradiation is a momentary removal process of the order of at most μsec, there is no risk of excess stress remaining in the vicinity of the processed part, and unlike mechanical recess formation, there is no effect on the back surface. It does not lower the space factor of the steel sheet.

Further, the waveform of the pulse laser used for processing the steel sheet of the present invention has a tail portion behind the initial spike as shown in FIG. In order to investigate the effect of this tail portion, the influence on the processing characteristics was examined while the length of the pulse tail portion was sequentially changed. As a result, high quality hole drilling can be realized even if there is no pulse tail portion, but if a pulse tail of 100 nsec or more is added, the adhesion of foreign matter to the periphery of the hole drilling site will be improved and the drilling quality will be further improved. I found out that It is considered that the effect of this pulse tail is to realize smooth hole drilling by heating and evaporating spatter generated by irradiation of the initial spike portion due to the reheating effect of the steel sheet by the tail portion.

Next, the effect of reducing the iron loss value was examined by changing the pitch of the recesses. The hole size and its positional relationship due to laser irradiation are determined by the laser repetition frequency and the laser beam scanning speed. FIG. 5 shows the hole diameter (d), the hole interval (p), and the hole machining ratio (R _dp ) which is the ratio thereof. R
_{When dp} = p / d and the hole diameter and the interval are equal, the hole machining ratio R _dp becomes 1. When the distance is half the hole diameter, the hole machining ratio R _dp is 0.5. The above-mentioned hole diameter 100-200μ
The following results were obtained when the hole machining ratio was changed for a hole having a depth of m and a hole depth of 10 to 30 μm. Hole processing ratio 1.0
The traces of the continuous pattern uniformly arranged as shown below are excellent in magnetic properties and have a clear iron loss improving effect, and those having a drilling ratio of more than 1 cannot obtain a sufficient iron loss improving effect. This is because if the hole machining ratio exceeds 1, the effect of the portion where no strain is introduced becomes large and the iron loss improving effect becomes unclear. As for the lower limit of the pitch in the plate width direction, there is no lower limit, as can be seen from the fact that the conventional tooth profile roll is used for continuous grooving. A pitch in the rolling direction of 3 to 10 mm is necessary for the irradiation interval to obtain the effect of reducing the iron loss value. If this interval is too wide, the effect of the portion where strain is not introduced becomes large and the iron loss improving effect becomes unclear. If it is too narrow, the magnetic flux density deteriorates, and the iron loss reduction effect tends to be unstable. It is considered that this is because if the strained region formed by laser processing becomes too dense, the magnetic domain subdivision becomes difficult to occur.

[0025]

The present invention will be described in detail below. A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, which has a characteristic that the iron loss value is improved without being lowered by the stress relaxation annealing of the present invention, will be described with reference to the configuration diagram shown in FIG. It was carried out. The laser discharge part 2 is a discharge excitation part of a continuous wave oscillation CO ₂ laser, and has the ability to obtain a laser output of 3 kW in a TEM00 mode when continuous wave oscillation is performed in a free running mode. Total reflection mirror 3 has a wavelength of 10.59
It is a ZnSe reflecting mirror which has been subjected to multilayer film vapor deposition having a reflectance of 99.8% in μm. Total transmission window 4 has a wavelength of 10.5
ZnSe window with anti-reflection coating at 9 μm. The confocal telescope 5 is composed of two ZnSe lenses having a focal length of 100 mm and having the same coating. The rotating chopper 6 is a metal blade that rotates at 60,000 rpm, and 10 to 1 is placed on the chopper blade.
00 slits are introduced. Therefore, the pulse repetition frequency is 10 to 100 kHz. The average output when the laser is oscillated in the free running mode under the above conditions is about 1200 W or more. The laser beam 1 extracted from the laser resonator is scanned by the polygon mirror 8 in the width direction of the steel sheet over 100 mm. When the laser beam 1 is focused on a point, a parabolic mirror 9 is used to form a steel plate 10.
It is focused on a 0.2 mm diameter beam on the surface of the.

Pulse repetition frequency 50 kHz, wavelength 1
A laser beam of 0.59 μm is condensed, and the pulse half width of the initial spike portion is 250 nsec, and the Q of the pulse tail is 2 μsec.
The switch CO ₂ laser pulse has a peak power density of 5 × 10 ⁷ W / cm ² at the initial spike portion and an average hole diameter of 20.
0 μm, the hole depth is 20 μm, the laser beam scanning speed in the steel plate width direction is set to 350 m / min, and the hole machining ratio is set to 0.
As No. 5, irradiation was performed at intervals of 6.5 mm in the steel plate rolling direction. As a result, a total iron loss improvement rate of 9% was obtained for the unirradiated material, and this value did not change even when stress relaxation annealing was performed. Furthermore, when the sample thus produced was molded into a wound iron core as shown in FIG. 6, good molding was possible without cracks during molding and voids during lamination.

[0027]

As described above, the characteristic of improving the iron loss value without decreasing by the stress relaxation annealing according to the present invention (S resistance)
A grain-oriented electrical steel sheet having RA property) can be manufactured by an iron loss improving method using a pulsed CO ₂ laser. As described above, since the grain-oriented electrical steel sheet has resistance to stress relaxation annealing, it can be applied to a material for a wound iron core, which cannot be applied to a conventional product by laser irradiation, and its application can be greatly expanded. Furthermore, even compared to steel sheets manufactured by a method using tooth profile rolls, which is a conventional method of improving iron loss having stress relaxation annealing resistance, the iron loss reduction rate is equivalent or higher, and the workability of wound iron core is better. It achieved such a result.

[Brief description of drawings]

FIG. 1 is an iron of a grain-oriented electrical steel sheet using a pulsed CO ₂ laser for producing a grain-oriented electrical steel sheet having a characteristic (SRA resistance) in which an iron loss value is improved without being reduced by the stress relaxation annealing of the present invention. It is a schematic diagram which shows the structure of the loss improvement method.

FIG. 2 is a typical measurement result example of an oscillation waveform of a Q-switch CO ₂ laser.

FIG. 3 is a conceptual diagram of cross-sectional shapes of a recess on the surface of the steel sheet of the present invention and a recess of a conventional method.

FIG. 4 is a conceptual diagram in the case of stacking conventional steel plates having a recess formed by a mechanical method.

FIG. 5 is a schematic diagram showing a pattern of hole processing and a hole processing ratio of the grain-oriented electrical steel sheet of the present invention by a pulsed CO ₂ laser.

FIG. 6 is a conceptual diagram of a wound iron core manufactured in an example.

[Explanation of symbols]

 1 pulse laser beam 1'laser beam input to polygon mirror 2 laser discharge part 3 total reflection mirror 4 ZnSe total transmission window 5 confocal telescope 6 rotating chopper 7 output mirror 8 polygon mirror 9 parabolic mirror 10 electromagnetic steel plate 11 Plane total reflection mirror

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takamichi Kobayashi 5-10-1 Fuchinobe, Sagamihara City, Kanagawa Nippon Electronics Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. A Q switch CO on the surface of a grain-oriented electrical steel sheet.
₂ The average diameter of the crater on the surface of the steel plate formed by irradiating the laser beam is 100 to 200 μm, and the depth is 10 to 30 μm.
The trace of a continuous pattern uniformly arranged so that the hole processing ratio (hole interval / hole diameter) defined by the hole diameter and the hole interval in the width direction of the steel plate is 3 to 10 mm and 1.0 or less in the rolling direction. And the back surface of the steel sheet is flat, and the grain-oriented electrical steel sheet is excellent in magnetic characteristics in which the iron loss value reducing effect is not lost even by stress relaxation annealing.